The presently disclosed embodiments relate generally to the flexible electrostatographic imaging members prepared to include the reformulation of a low stress/strain protective layer which provides not only superb wear/scratch resistance, but also renders the resulting flexible imaging members with flatness to meet the functional requirement of electrostatographic imaging apparatuses. More particularly, the embodiments pertain to the flexible multi-layered electrophotographic imaging member belts prepared to comprise plasticized imaging layer(s) and also include a low stress/strain anti-curl back coating formulated to provide a wear/scratch resistance film forming A-B diblock copolymer and a plasticizer to impart flexible imaging member curl control.
Flexible electrostatographic imaging members are well known in the art. Typical flexible electrostatographic imaging members include, for example: (i) electrophotographic imaging members (photoreceptors) commonly utilized in electrophotographic (xerographic) processing systems; (ii) electroreceptors such as ionographic imaging members for electrographic imaging systems; and (iii) intermediate toner image transfer members such as an intermediate toner image transferring member which is used to remove the toner images from a photoreceptor surface and then transfer the very images onto a receiving paper.
The electrostatographic imaging members are known to be in two configurations, for example, in flexible and in rigid configurations. The flexible electrostatographic imaging members may either be seamless or seamed belts. A flexible seamed imaging member belt is usually formed by cutting a rectangular imaging member sheet from a web stock, overlapping a pair of opposite ends, and welding the overlapped ends together to form a welded seam belt. Typical electrophotographic imaging member belts that include a charge transport layer and a charge generating layer on one side of a supporting substrate layer exhibit undesirable upward curling. Thus, an anti-curl back coating is usually coated onto the opposite side of the substrate layer to render imaging member belts flatness. A typical electrographic imaging member belt includes a dielectric imaging layer on one side of a supporting substrate. An anti-curl back coating is often needed on the opposite side of the substrate for curl control and render desired flatness. However, since the rigid electrostatographic imaging members utilize a rigid substrate support, no anti-curl back coating is needed for curl control.
In electrophotography, also known as xerography or electrophotographic imaging, the surface of an electrophotographic plate, drum, belt or the like containing a photoconductive insulating layer on a conductive layer is first uniformly electrostatically charged. The imaging member is then exposed to a pattern of activating electromagnetic radiation, such as light. Charge generated by the photoactive pigment moves under the force of the applied field. The movement of the charge through the photoreceptor selectively dissipates the charge on the illuminated areas of the photoconductive insulating layer while leaving behind an electrostatic latent image. This electrostatic latent image may then be developed to form a visible image by depositing oppositely charged particles on the surface of the photoconductive insulating layer. The resulting visible image may then be transferred from the imaging member directly or indirectly (such as by a transfer or other member) to a print substrate, such as transparency or paper. The imaging process may be repeated many times with reusable imaging members.
For a conventional negatively charged electrophotographic imaging member in flexible configuration, it is comprised of a single photoconductive/imaging layer (or compounded layers) that is (are) solution coated over the top of a thick flexible substrate support layer. In these flexible multiple-layered electrophotographic imaging member manufacturing processing, the charge transport layer (CTL) is coated over the charge generation layer (CGL) by applying a CTL coating solution directly over the CGL, then subsequently drying the wet applied CTL coating at elevated temperatures of about 120° C., and finally cooling down the coated imaging member to the ambient room temperature of about 25° C. Due to the thermal contraction mismatch between the CTL and the substrate support, the processed imaging member web (with finished CTL coating obtained through drying/cooling process) spontaneous curls upwardly into a roll. In these imaging member designs, the CTL has a typical coefficient of thermal contraction of from about 3 to about 4 times, or approximately 3.7 times, greater than that of the flexible substrate support. As a result, the CTL has a larger dimensional shrinkage than that of the flexible substrate support after through the process of application of wet CTL coating, drying it at elevated temperature, and the eventual imaging member web cools down to the ambient room temperature. The exhibition of imaging member web curling up after the completion of CTL coating and cooling down to room ambient is due to the consequence of larger CTL dimensional contraction than the substrate support as a result of the heating/cooling cycles of the manufacturing processing step To offset the curling, an anti-curl back coating (ACBC) is applied to the backside of the flexible substrate support, opposite to the side with a CTL, and render the imaging member web with desirable flatness.
But inclusion of an ACBC in the conventional negatively charged flexible imaging member incurs material cost, adds labor involvement, and also reduces imaging member product throughput, so activities devoted to ACBC elimination have been pursued. In the most recent negatively charged flexible electrophotographic imaging member improvement/development and break through, structurally simplified imaging member designs (with the elimination of an anti-curl back coating) have been successfully created and demonstrated through CTL plasticizing approach. Although the fabricated ACBC-free flexible imaging member on one hand is found to produce excellent photo-electrical functioning stability result as well as copy print out quality improvement advantages, it does, unfortunately, create an undesirable consequence because the surface of the bottom exposed substrate support layer (without the protection of an ACBC) is highly susceptible to the development of pre-mature onset of wear/scratch failure against the machine belt module support rollers and backer bars sliding mechanical friction action under a normal dynamic belt cycling machine operation condition. For belt use in the high volume elctrophotographic imaging machines and printers (utilizing large numbers of belt support module rollers and backer bars), substrate support exposure (without ACBC covering) in the ACBC-free imaging member belt has been found to cause early onset of substrate wear-off problem. Substrate support wear is very pronounced causing generation of large amount of debris and/or dust particles inside the machine cavity to adversely impede proper imaging member belt functional operation. Since the early development of substrate support layer wear-off to generate debris and/or dust particles inside the machine cavity, the debris/dust eventually deposits onto various machine subsystems and components which thereby interfere and adversely affect the electrophotographic imaging process and degrade the dynamic imaging member belt cyclic motion quality. As a result, frequent and costly premature imaging member belt replacement is required in the field.
Moreover, the ACBC-free imaging member prepared by relieving the CTL internal stress/strain through incorporation of plasticizer does not provide an entirely flat configuration which still does not meet the high volume machines imaging member belt flatness requirement.
The term “substantially flatness” or “nearly flat” refers in particular to an ACBC-free flexible negatively charge imaging member prepared to have the CTL incorporated with a plasticizer in its material matrix for effecting internal stress/strain reduction to give nearly flat configuration; that means the prepared imaging member exhibits an upward curling of at least equals to or greater than 14 inches in diameter of curvature.
Therefore, the known structurally simplified ACBC-free imaging member design exhibits deficiencies and shortfalls which are undesirable for use in advanced high volume automatic, cyclic electrophotographic imaging copiers, duplicators, and printers. To maintain the benefits offered by the imaging member containing a plasticized CTL and also resolve its associated issues, a novel ACBC design is now provided. More specifically, the present embodiments provide the imaging member with a re-designed ACBC reformulation having improvements of reduction in surface contact friction, less susceptibility to scratch/wear failure, and as well as rendering the prepared imaging member with absolute flatness. To achieve this purpose, flexible imaging members in various embodiments are prepared to contain a plasticized CTL and include an ACBC reformulation designed to comprise a high molecular weight film forming high molecular weight A-B diblock copolymer, adhesion promoter, liquid plasticizer, and organic or inorganic particles dispersion in the material matrix according to the descriptions of present disclosure.